1. Field of the Invention
The present invention relates to a water purification system, and more particularly to an automatic sanitizing system and a method for maintaining in a water feature a sanitizing agent concentration within a desired range.
2. Description of Related Art
Portable self-contained spas have become popular in recent years. Such spas are easy installed and powered by existing electrical lines or dedicated electrical hook-ups.
Once installed, the homeowner must sanitize the spa to prevent the proliferation of disease-causing micro-organisms. Typical spa maintenance requires adding granular sodium dichloro-isocyanurate as a sanitizing agent to control such bacteria growth. Bromine alternatively can be added as a sanitizing agent. Bromine preferably is used as the sanitizing agent in the spa because it remains in liquid form at 100.degree. F., unlike chlorine.
Many spa owners today, however, do not properly maintain their spas. Some owners do not adequately sanitize their spas despite the danger of unhealthy bacteria growth. Other owners over-sanitize their spas which can damage spa equipment, including the heater and the spa shell.
In an effort to ease spa maintenance so as to avoid both under- and over-sanitizing, some prior systems have automated at least part of the maintenance. For example, an automatic demand chlorination system is disclosed in U.S. Pat. No. 4,657,670 for use with a recirculation unit for a swimming pool. The automatic demand chlorination system has a dry chlorinator which feeds chlorine into the water if a chlorine need is detected by a sensing unit. An oxidation-reduction type sensor is used in the automated system for this purpose. Although oxidation-reduction type sensors have been used to measure the concentration of halogens used as sanitizing agents in water features there are some limitations, e.g., a nonlinear response to variations of halogen concentration or a required calibration to changing starting points.